Microscope Museum

Collection of antique microscopes and other scientific instruments

Pair of Antoni van Leeuwenhoek aquatic/eel viewer microscope replicas, EXEMPLAR EX LONDINIO MMXXV (2025)

Antoni van Leeuwenhoek (1632 - 1723) was a Dutch microscopist who was the first to observe bacteria and protozoa, and is many times referred to as the father of microbiology. Van Leeuwenhoek made microscopes consisting usually of a single high-quality lens of very short focal length. At the time, such simple microscopes were preferable to the compound microscope, which increased the problem of chromatic aberration. Van Leeuwenhoek’s methods of microscopy remain something of a mystery. During his lifetime he made more than 500 lenses, most of which were very small (no larger than a pinhead) and usually mounted them between two thin brass plates, riveted together. A large sample of those lenses were found to have magnifying powers in the range of 50 to, at the most, 300 times. This is a pair of replicas of an antique Antoni van Leeuwenhoek microscope, made in April 2025, illustrating a quite unusual aquatic/eel viewer type of microscope made by Van Leeuwenhoek. The replicas are made of brass and contain a single lens enclosed within two brass plates riveted together. Both replicas are engraved with “EXEMPLAR EX LONDINIO MMXXV”. One replica is also engraved with the Roman numeral “I”, and the other replica with “II”. This type of microscope would have been used by Van Leeuwenhoek to observe the passage of red blood cells through the capillaries in the tails of living fish and eels, and to demonstrate such observations to his many visitors. To use this microscope, the specimen was placed head down in the glass tube containing water. The glass tube was held in place with the use of springs, allowing it to move backward for focusing by adjusting a screw against the glass. The process to build and use this microscope was described in detail by Van Leeuwenhoek himself in a 1689 letter to the Royal Society of London (Figure 1). Two images of this microscope type can be also identified on the cover image of the 1747 auction catalogue when all Van Leeuwenhoek’s little lenses and microscopes were sold after the death of Van Leeuwenhoek’s daughter Maria, and 24 years after Van Leeuwenhoek’s death (Figure 2 – see white arrows, and the enlarged images of the microscopes). Unfortunately, no surviving microscope of this type is known to exist today, but a replica can be found in the Rijksmuseum Boerhaave in Leiden (object number V16925). Van Leeuwenhoek made and used other types of microscopes to observe and study different types of samples, including his most well-known single-lens microscope, dual- and three-lenses microscopes, and other eel/fish viewers. Figure 3 below shows a selection of replicas of these microscopes making part of this collection.

Figure 1. Part of a figure that appeared in a letter sent by Van Leeuwenhoek to the Royal Society of London in January 1689, showing the components and layout of his eel viewer microscope. The figure included an illustration showing an eel in the tube (right).

Figure 2. Cover image of the 1747 auction catalogue when all Van Leeuwenhoek’s lenses and microscopes were sold after the death of his daughter Maria. The white arrow points to eel viewer microscopes, which are enlarged on the right images.

Figure 3. Replicas of different types of microscopes associated with Antoni van Leeuwenhoek: (A) Standard type of single-lens microscope; (B) Dual lenses microscope; (C) Three-lenses microscope; (D) Aquatic/eel viewer microscope; (E) Eel viewer/showcase for visitors microscope; and (F) Fish viewer microscope. All these replicas are engraved with “EXEMPLAR EX LONDINIO MMXXV”.